The deaf or hearing-impaired that cannot hear well enough to use the telephone use communication terminals to converse over telephone lines. Such terminals are referred to as telecommunication devices for the deaf, or TDDs, and are comprised of a keyboard and display. TDDs are connected to a telephone line through a modem which allows the terminal to transmit information over a telephone line to another electronic device which is connected to the telephone line through another modem. When characters are typed by a first party on the keyboard of a first terminal, tones corresponding to the characters are transmitted via the modem through the telephone line to a second terminal. At the second terminal, the tones are received by a second modem and converted back to characters to be read by a second party. In this manner, a conversation proceeds by the taking of turns by each of the users in the typing back and forth on the TDDs. In order to have a TDD conversation, however, both parties must have a TDD.
It is often necessary or desirable for a TDD user to call a telephone number that is not equipped with a TDD. These calls may be either emergency or non-emergency, e.g. telephone calls to police, employers, doctors, repair and maintenance workers, relatives and loved ones, etc. In order to make possible telephone calls between a TDD user and a non-TDD equipped telephone number, TDD relay centers have been established in many locations. A TDD relay center receives telephone calls from TDD users who request, via TDD, for a relay operator to place a call with a second party for them. The relay operator then calls the second party and tells the second party what the TDD caller is typing. When the second party talks, the operator then types back to the TDD caller. Conversely, a call through the relay center may originate from a non-TDD user wishing to communicate with a TDD user. The call then proceeds in the same manner.
Calls placed through a relay center can be frustrating in that they are slow and lack privacy. Those people that can speak, but not hear, may prefer to talk directly to the other party and have the operator type back the response. Similarly, a speech impaired caller would rather listen for themselves rather than have the operator interpret.